Effects of bone lengthening on surrounding tissues
Gradual bone lengthening has a negative impact on the surrounding muscles through stretch, impalement by pins and wires, pain and inflammation. The speed of the gain in length during callotasis with a 1-mm/day rate is about four to eight times faster than during the adolescent growth spurt with its temporary muscle shortenings [8].
No wonder that the clinical challenges of muscle distraction and subsequent decrease of adjacent joint range of motion go in parallel with the amount of lengthening. This is reflected by histological changes after lengthening of more than 30 % of its original length [22, 116–119], as the whole muscle from origin to insertion is stretched [81]. The elastic limit of stretched muscles (strength–strain curve) is 10–15 % of the length at rest. Excessive stretch leads to plastic deformation and subsequent contractures, which commonly affect muscles spanning two joints (rectus femoris, hamstrings). There are only few data about the loss of muscle power during the distraction–consolidation process and the speed and amount of recovery thereafter. There is a small residual decrease in muscle strength and power after surgical lengthening without any impact on the activities of daily living [120]. Pre-operative muscle training as a preventive measure and a post-operative intense rehabilitation programme including continuous passive motion, extension splint, strengthening and stretching exercises, as well as proprioceptive training, are mandatory until the pre-operative level is reached [66]. Nerves and vessels adapt in length during the distraction process and recover from temporary degenerative changes within 2 months after the halting of distraction [104].
Excessive gradual (>20–30 %) or acute distraction (>15 %) may both lead to partial or complete loss of nerve potentials [121, 122].Joint cartilage may be exposed to reactive forces which increase linearly with distraction [123]. In addition, non-weight-bearing and decreased range of motion diminishes nutrition of the cartilage and may support histological
changes which appear after 30 % lengthening in animal experiments [124, 125].Physeal cartilage shows experimental histopathological changes secondary to increased axial load [124]. However, alterations of the growth rate were never observed in a clinical setting [126].
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3364349/
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